1. Related Technical Fields
Related technical fields include map information distribution systems, methods, and programs that distribute update information for updating map information from a map information distribution center to a navigation device.
2. Related Art
In recent years, a navigation device is frequently installed in a vehicle to execute guidance for driving the vehicle, so as to make it possible for the driver to reach a desired destination easily. The navigation device is a system that is capable of detecting the vehicle's current position using a GPS receiver or the like, then obtaining map data that corresponds to the current position from a storage medium such as a DVD-ROM, hard disk, or the like, or through a network, and displaying the map data on a liquid crystal display. In addition to reading the map data that includes the vehicle's current position from the storage medium or the like, drawing a map image of the area surrounding the vehicle's current position based on the map data, and displaying the map image on a display system, the navigation device displays a superimposed vehicle position mark on the map image, then scrolls the map image as the vehicle moves or keeps the map image stationary and moves the vehicle position mark, such that the driver can tell at a glance the location where the vehicle is traveling.
New roads are built every year all over Japan. As a result of such construction, an existing road may be eliminated or the path of the existing road may be changed. Accordingly, map data recorded in the navigation device must be updated at somewhat regular time intervals. The updating of map data in such case may be performed by purchasing a new DVD to replace an old DVD, writing map data to the hard disk at a store, or overwriting hard disk content based on map data distributed from a map information distribution center or the like.
There are various map information distribution systems proposed that automatically distribute from a map information distribution center to the navigation device update information for updating map data recorded in the navigation device.
For example, the version of the map information currently held in the navigation device may be sent from the navigation device to a map information distribution center. The map information distribution system is structured such that the navigation device subsequently receives update information for updating map information from the map information distribution center, and updates the map information based on the received update information. Thereafter, the navigation device visibly displays an updated section and a non-updated section, as well as an update timing order, so that these are distinguishable (see Japanese Patent Application Publication No. JP-A-2005-91225, paragraphs [0013] to [0040] and FIGS. 1 to 3 for an example).